Yahoo! Not Done Acquiring (Correction)

This story was originally published June 5, and has been corrected to reflect the fact Gowalla was acqui-hired by Facebook, in 2011, then shut down. TheStreet regrets this error.

NEW YORK ( TheStreet) -- Apparently all of that cash on Yahoo!'s ( YHOO) balance sheet is burning a hole in Marissa Mayer's pockets, because she's not done acquiring companies.

Despite having just spent $1.1 billion to acquireTumblr and rumors that it has its eye on Hulu, Yahoo! very well could be looking to getting into the check-in space, according to CFO Ken Goldman.

Goldman spoke at a investment conference, and continued to sound the horn that Yahoo! is not done acquiring companies in the mobile space. He noted "localization of the space," which sounds an awful lot like check-in services.

I've opined before that Yahoo! would acquire Yelp ( YELP), which not only lets people check in to restaurants, stores and local businesses, but also provides search and content.

Mayer has continuously alluded to the fact that Yahoo! needs "more personalized content and increased product innovation" to get the Internet giant back on track for Display revenue growth. Yelp isn't profitable yet, but revenue growth is soaring, up 68% year-over-year, according to Yelp's latest earnings report.

At a market cap approaching $1.8 billion, Yelp is now probably too big for Yahoo!, especially after the Tumblr acquisition, but that doesn't mean there aren't other alternatives.

Foursquare certainly would be at the top of any M&A list for check-in services. There's been questions about how Foursquare, run by Dennis Crowley can generate revenue, but the company recently raised $41 million in financing, so investors must see something about the company's future.

The optimism surrounding Yahoo! right now is extraordinarily high, and the market is reflecting that. Shares are up 31.3% year-to-date, and more than 70% since Mayer took over the top spot in Sunnyvale, Calif. She has certainly been acquisitive since taking over Yahoo! and reshaping the company in her vision, having bought Stamped, a mobile review site, Snip.it, an online content organization company, OnTheAir, in addition to Tumblr.

A check-in app would continue Mayer's radical transformation of Yahoo! into the world's "daily habit," as she has so often put it. With Tumblr, and the potential acquisitions of Hulu and perhaps a check-in app, Yahoo! is fast becoming the go-to place in Silicon Valley for high-profile acquisitions.